First Study to Look at Muscle Strength in Patients with Disc Herniation
We know that patients with low back pain (LBP) of unknown cause have weaker trunk and knee strength. Is this also true for patients who have lumbar disc herniation (LDH)? Does sciatica cause leg weakness on one side or in both legs? These are the questions asked by researchers in this study.

Strength of trunk muscles and both knees was measured for LDH patients with and without sciatica. Results for all patients with LDH were compared to healthy volunteers (the control group).

Researchers found much lower muscle strength in trunk and knee motion for the LDH patients. This was true with fast or slow movements. There was no difference in strength between the sciatica and non-sciatica legs in the LDH group. Both sides were weak.

The authors say the weakness doesn't seem to be coming from the effect of the LDH on muscles. Patients with nonspecific LBP have the same weakness. It may be that pain in the back and legs leads to physical disability and muscle atrophy.

Weakness is the final result of both. Fear of pain may add to the problem. Patients stop moving normally when they're afraid it's going to hurt.

This was the first study to look at the effect of LDH on both trunk and leg muscle strength. Future studies are needed to help explain the results. Scientists will attempt to find out what the exact mechanism is for decreased strength of trunk and both legs in patients with LDH. This information may help prevent such problems for LDH patients.
References
Cheng-Wen Ho, MD, PhD, et al. Isokinetic Muscle Strength of the Trunk and Bilateral Knees in Young Subjects with Lumbar Disc Herniation. In Spine. September 15, 2005. Vol. 30. No. 18. Pp. E528-E533.